Manual to automatic system



Dec. 6, 1927. 1,651,401

R. MERCER ET AL MANUAL TO AUTOMATIC s ys'rEm Filed May 9, 19 7 SheetsJ-Sheec 1 mum Dec. 6, .1927. 1,651,401

7 v R. MERCER ET AL MANUAL TO AUTOMATIC SYSTEM Filed May 9, 1924 7 Shee set 2 Irwin-TIFF? Ewharfi 1 12mm- Frank TBrmh Dec. 6, 1927. 1,651,401

R. MERCER ET AL MANUAL TO AUTOMATIC SYSTEM 1 File May 9, 1924 '7 est 3 k 1 '1'z uEnZurs Jimhard Planar-Frank Tan/.1

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Dec. 6, 1927.

R. MERCER ET AL MANUAL TO AUTOMATIC SYSTEM 7 Shee Filed May 9 192 InUEn UTE Ezchard FYEMEP Frank T EHEZ'Z Dec. 6, 1927.

- R. MERCER ET AL MANUAL TO AUTOMATIC SYSTEM 7 She Filed May 9, 1924 InUBn ME; I Fmhard MET/3151" Frank TEnch Dec. 6, 1927.

1 651,401 R. MERCER ET AL MANUAL TO AUTOMATIC SYSTEM Filed May 9, 1924 I 400 [rm Emharzi Mar/:21" Frank Tzmrh Dec. 6, 1927. 1,651,401

R. MERCER ET AL MANUAL TO AUTOMATIC SYSTEM Filed- May 9, 1924 '7 sheets sheet 7 #555515? I Ewhard Pia r1351" Fz"ank T511521.

Patented Dec. 6, 1927.

RIonAnn ME CER," F marrow, Am: ERA NK ai'EiIo'H, 0E wEs'r nonwoon, LONDON,

ENGLAND, As'sIoNoRs,

I 'TBY 'M'E'snE'Ass GNMENTs l'roA ToMATIo ELECTRIC me, on CHICAGO, ILLINOIS, A CORPORATION 01 DELAWARE. 1-.

' AnuaL re-AUTOMA IC 5 5 Application filed May 9,1924, seria wmvusss; and in Great Britain May, 31,1923.

' The present 'invention concerns improvements in or relating to telephone systems and more particularly to those systems in which calls are set up froma manual subscriber over numerical. switches controlled by an operator. In systems of this 'kind it is desirable in order that each operator. may be able toworkat 'full speed that she shall be able to make use of a plurality of impulse senders ata time, say 'threeor four. 1f this-is done it becomes very uneconomical to provide thejrequired numberlof Yinipulse senders individual to each operator and accordingly they are: arranged in large groups accessible'in commonto anumber of operators. The main object of the invention is to provide improved circuit arrangements for associating an idle impulse sender with a trunk line' and forcontrollin-g it'so as to set up thedesired connection.

According to one feature of the invention, on an operator performinganoperation; in connection" with the "selection of. an idle line, an idle link circuit. becomes associated with the operators key set, the line selected and an idle'impulse sender.

Anotherfeature of the invention is that an operators key .set is associatedgwith an idle link circuit over] a forwardly hunting switch, the said link-circuitbeing associated with a trunk line byan operation on therpart of the operator and with an idle impulse sender by the operatioirof a hunting switch".

-A further feature is that an o erators key set'is associated withfanidle lin circuit over a forwardly hunting sw1tch, sa1d hnk circuit being .associatedby an operation on i i the part ofthe operator withboth. theselected trunk line and an idle impulse sender.

Other features relate to. an improved cir cuit' I arrangement for automatically initiat ing the generation of .irnpulsesuafter all the digits have been stored and to an improved holding circuit whereby an-impulsesehder may be, controlledjfrom the selected line over the link circuit switches. 1

These features and others not specifically mentioned atthis point will be more ftully appreciated from the following descriptiontaken in COHJIlIiCillOH with the accompanying: drawings.

' only..and-tliat various modifications may be .."In-Figure"1 is general layout of the apparatus used in extendmg a connection from a manual sub? It should be understood that the czr-bodiment described is by wayxof example made" in the individual circuits without exceedingv the scope oiithe invention.

Referr1ng:n0w-..to the drawings, Fig. 1 is a general layout ortrunkingdiagram; Figs.

2, 3, and 4 show by means of theusual circult diagrams one embodiment of the circuit arrangement employed in connection with the layout shown in Fig. 1'; and Figs.

5,6, and 7 show a desirable modification of the arrangementshown in Figs. 2, 3, and 4.

link circuits, together with the switch for connecting the link circuit with an idle register sender; andwFigit shows one of the register senders. J

In the modification :shown in- Figs. 5-7, Fig. 5 corresponds to Fig. 2; Fig. 6 corresponds to Fig. 3 and Fig. 7 corresponds to shown, .as above stated; the

scriber to an automatic subscriberbyway of the mechanical tandem operators i position operators link -circuits, -and also one oftheand this operation will be briefly described. it a W'hen the subscriber "initiates a call, the A operatorat the manual exchange issignalled in :theusual manner and she thereupon inserts the answering'plug P ofthe cordcircuit O, for instariceyiri the jackgJ "Upon learning the subscribersrequirements, she will give the required number to theB op erator' over: an order wire which is not shown. She will then be assigned a junce tion lineffor instance, the junction line L and will thereupon insert the plug P into the jack-J When the B operator presses the assignment-key corresponding to the line L which-she has assigned, the sender selector SS, corresponding to. the outlet with which the wipers ofthe' outlet finder.

OF arein engagementwill hunt to find an idle set of impulse sending equipment which thereupon becomes associated with the key set K. The B operator will then set up the number. on the key'set and in accordance with' theifirst digit, the first storage relay group'fsR will be influenced:=over the outletfiiiderinithe position: shown, back contact and armature T sender selector SS armature W and its back contact, back contact and armature Z and transfer switch TS in first position. The transfer switch TS is moved one step as each key 15 released so that the various digits are recorded on the appropriate sets of storage relays SR SR SR SR When the B operator presses her start key (assuming that the plug P has already been inserted in the jack .L), the armature '17,, 1V, and Z will be operated so that the storage relay sets are connected by way of con; verting relays CR to the impulse semici- IS and this latter is connected to the corresponding junction line by way of the connecting point 0,. The required impulses are then sent out by the impulse sen'er as controlled by the storage relays and these impulses will operate the selector E and snicoeeding selectors and a connector (not shown). The transfer switch is moved on one step at the end of each train of impulses and thus the appropriate storage relay set is brought into operation to control the gen eration of each successive digit- The outlet finder OF is moved on one step when the start key is pressed; consequently the key set K is then associated with another outlet and the operator may cmnmence setting 11 another connect-ion, as soon as she has finis ed with the previous one. 1

Since in the arrangement shown four outlets are provided, the sending of impulses may take three times as long as the actual setting u of the number withoutthe op erator being held up owing to lack of outlets. 1

Referring now more specifically to Figs. 2, 3 and 1, the operation involved in the sending of a call will be traced through in detail. The A operator in the manual exchange after ascertaining the calling subscribers wishes will communicate with the B operator at the mechanical tandem exchange over an order wire which not shown. The B operator will thereupon assign to the A operator an idle inter-exchange trunk, for instance, that comprising conductors 1 and 2, at the same time pressing the corresponding assignment key 3. The effect of this is to energize the assignmentrelay at which thereupon closes its contacts 5, '6, T, 8 and The closing of the contacts 5, (i, T and 8 Jrepares circuits for the relays 10, 11, 12 not 13, respectively, while at contact 9. earth is connected to lead over back con tacts and armatures such as 9 and 19 on all the other assignment relays in the position,

A circuit is thereupon completed from this earth over lead 100, through relay 109, wiper 113 and the contact on which it is standing, normally closed spring 1140f the sender disconnect key, armature 121 and its back contact and through relay to battery. Relays 120 and 109 energize in series in this circuit and the latter at contact 120 opens a point in the circuit of the driving magnet 123, another point in which circuit is closed at armature 125 by relay 108 which is also energized by earth on lead 100. As, however, relay 108 is slightly slow to pull up, this circuit for driving magnet 123 is never completed in the normal working of the a )paratus even should earth be con meet to lead 170, which will not always be the case. Relay 120, upon energizing, at armature 1 31 completes a circuit from earth at armature 140 for driving magnet 162 and cut oil relay 119 in series and at arn'iature connects test wiper 110 to the junction of relay 119 and magnet 102 by way of armatnres 132 and 161 and their resting con tacts. In case the wiper 110 icsting on a contact associated with an idle sender, there will be no earth present on this contact and relay 119 will at once energize. It, hovvever, the wiper 146 finds earth on the contact with which it is in engagement relay 119 will be short circuited and the driving mag net 162 will be energized and will operate intermittently under the control of its interrupter contact 163 to step the wipers 143-146 inclusive, around until wiper encounters a contact which is not earthed. When this occurs, relay 119 is no longer short circuited and energizes in the following circuit: battery, stepping magnet 102, interrupter contact 163, winding of relay 119, front contact and armature 131, back contact and armature 140, earth. Relay 119, upon operating, at armatnrcs 12-7, 128 and 130 connects the wipers 110, 111 and 112 through to the wipers 1.43, 1.41 and 11-115, respectively, by way of back contacts and armatures 136, 137 audit-l8. At armature 1323, relay 119 shunts contact 131 so as to complete a locking circuit for itself, at armature 132 opens the circuit of the driving magnet 162 and places earth on the test wiper 14d, and. at armatures 129 and 131 connects battery and earth respectively to leads 102 and 103 extending to thetrunk circuit.

The earth connection to lead 103 is by way of the normally closed spring 117 of the sender disconnect key and a connection from thisalso extends to the sender guard lamp 164 which thereupon lights to show that the outlet is in use. The cii'ect of connecting battery and earth to leads 102 and 103 is to complete an energizing circuit for relay 10, which circuit may be traced from battery on lead 102, normally closed springs controlled by armature 16, winding of relay 10, armature 5 and its working contact to earth on lead 103. Relay 10 upon operating, at armatures 14 and 18 connects the outgoing trunk line to the impulsing leads 105 ment lamp 27, at armature' 16 opens its initial energizing circuit and completes a locking circuit for itself by way of normally closed contact 26 controlled by the busy'or cancel key, and at armature 17 shunts armature 5 so that its circuit may not be opened when the assignment relay falls back as it does .When the assignment keyis released. The, operator keeps the" assignment. key pressed until the assignment lamp 27 lights whereupon she knows that the outlet finder and sender selector switches have functioned correctly'and that her key set is now connected through to anidlesetof impulse sending equipment. The time required for this operation to take place will in general be very small; probably in most cases the operator would naturally press the key sufliciently long.

The operations which have so far taken place are, therefore, the association of th'e.

single set of digit keys with an idle impulse sender by way of an idle outlet and'the preparation of the association of this impulse sender with .the trunk line assigned. The operator may now therefore proceed to set up the wanted number on the digit keys, which number we will suppose for the sake of example is 8645321. I 1

'.When she 'presses the key 8 a circuit is completed from earth, resistance 147, .contact of key 8, lead 170, wiper'lll, working contact and armature 128, resting. contact and armature 137, wiper 144, lead166,.armature249 and its resting contact, winding of relay 204, winding of relay 203, battery. Relay 203 is. marginally adjusted and does not energize unless dead earth 'isconnected to vlead 166 but relay. 204' energizes at .this

time and at armature. 219 completes a circuit as follows: earth,winding of relay 201, back contact and armature 208, armature 218and its back contact, armature 219 and its front contact,;back contact and armature 214, wiper 22 7 andfirst contact of the transfer switch, lead 263,:relay 231 to. battery. Relays 201 and-231 energize' in this circuit and relay 201 at armature "210' completes a circuit for. relay 200fas follows: earth, working contact and armature, 223 of the operated relay: 204, workingco11tact and armature 210, winding of relay 200. to battery. Relay' 200 operates, at armature 208 opens the circuit. for. relay 201 which thereupon de-energizes,. at armature 209 completes a locking circuit for'itself and at armature 211 closes a circuit for the stepping magnet 245 of the transfer switch which that. it does notrelease when its initial en ergizingcircuitis opened-at armature 208, atxarmature 239;opens a circuit for the is not released when the switch steps oft normal and the off normal contact 247 closes, and at armature243closes a point in a chain circuit the purpose of which willbe described fully hereinafter.

The operation of the digit key 8 also closes the following. circuit: earth, operated spring of key 8,.lead 171, wiper 110 and the contact with which it is in engagement, working contact. and armature 127 resting contact and armature 136, wiper 143, lead 165, armature 247 and its resting contact, winding of relay 206, winding of relay 205 to battery. Relay205is marginally adjusted in the same manner as relay 203 but as dead earth has been connected to the energizing lead, both relays 205 and 206 energize in series. Relay 206 upon energizing, at armature 224 prepares a circuit for relay .200 and at armature 221 closes a point in the circuit over the wiper 225, which circuit however is not completed owing to another point being opened at the back contact of armature 220. Relay 205 at the front contact of armature 220 completes a circuit as "follows: earth, relay 201, resting contact and armature 208, armature 220 and its working contact, resting contact and armature 213, wiper 226, first contact of transfer switch, lead 262, relay 230 to battery. The operation of relays 200 and 201 which will be produced by relays 205 and 206 is the same as produced'by the operation of relay 204 which has already been described. Relay 230, upon energizing at armature 242 closes another point in the chain circuit, at armature 238'opens another point "in the auxiliary release circuit and at armature 234 locks itself up .tothe earthed lead 168,'at the same time connecting earth to the first contact in the bank of wiper 5226.- a 1 i 7 It will be noted that as long as the operator holds the digit key 8 depressed, the circuit of relay 200 will be maintained over its own locking contact 209fand contacts 223 and 224 in parallel. 'As soon, however, as the key is released, relay 200 deenergizes and at armature 211 opens the circuit of the stepping magnet245' which thereupon advancesthe wipers 225-228 inclusive into engagement with the second set of'bank con tacts.

When the operator presses the key-6 in accordance with the nextdigit, circuit is completed from earth, resistance 147, lead 171, wiper and the contact with. which it is in engagement, working contact and armature 127, resting contact and'armature 136, wiper 143, lead 165, armature 247 and its resting contact, relay 206, relay 205'to battery. =Since relay 205 is 'marginally ad'- justed, relay 206 alone energizes in this circuitand aicircuit is thereby completed from earth at relay 201, back contact and armaturc 208, armature 220 and its back contact, armature 221 and its front contact, hark contact and armature E312, wiperflzfi and the second contact in its bank to battery through relay 265 in the second digit storage set. At the same time a circuit eompleed from resistance earth over the springs of the 6th digit key, lead 170 and lead 100 for relays 203 and 204, in consequence of which relay 201 energizes and completes a cir; nit: over wiper 227 tor relay Clearly the operation of relays E200 and 201 will be the same in this case as has been previously described and when the digit key (3 is released, the transfer switch will he stepped on so that the wipers engage with the third wt of contacts.

\Vhen the operator presses the digit key t tor the next digit, a circuit is completed from earth. resistance 147., spring of key -31, lead 100, wiper 112, working contact and armature 130, resting contact and armature 138, wiper 145, lead 107, armature 250 and its resting contact to relay 202, A branch of this circuit also extends through resistance 251 to the relay 260, but relay 200 is adjusted so that it will not energize in series with both resistances 117 and. 251. Relay 202 is energized, however, and at its contact 217 completes the usual circuit tor relay 201 which will extend over back contact and armature 215, ha-r228 and the third contact of its bank to relay 207.

The circuit changes which take plate in setting up the remaining digits will be readily understood from what has already been said, the general operation being that one or more of the relays 202-t3 operated and in consetpience of this, circuits are conn'ilcted over the wipers of the transfer switch tor one or more of the relays in the appropriate storage sets. Relay 5200 always remains energized as long as a digit key depressed and when the key is released it (lo-energizes and brings about the advancement of the switch wipers into engagement with the succeeding set of bank contacts.

When the operator has set up the complete number she will press the start key 150. The effect of this twofold: In the first place a circuit is completed for the driving magnet 123 which thereupon operates to step the wipers 110113 inclusive, of the outlet tinder one step so as to associate the key setwith another outlet. In the second place a circuit is completed for the start; relay 1:31, which thereupon energizes and closes its mutants 15552.. 1:33, 154 and 155. In any one case, however, only one of these contacts can be usefully operative; in the present case, a ci rcnit is completed from battery, resistance 150, armature 155 audits working contact, winding 01 relay 121, resistance 14.1., armature 132 and its Working contact, Working contact and armature 131 to earth. Relay 121 is provided with a light armature 1691 which 15 operated alone when the relay is energized in series with resistance 1411 and by shunting armature 155 serves to maintain the battery connect-ion after the start key 150 has been released and the start relay 151 deenergized.

It has been assumed in the foregoing that the A operator in the originating manual exchange has not yet plugged in on the trunk line assigned to her when the B operator presses her start key. An examination of the circuits will show, however, that it is immaterial Whether the A o mrator plugs in or the B o )erator presses her start key first and that the sending o1 impulses Will commence when both these actions have taken place irrespective of which preceded the other. The A and 13 operators may thus work independently in completing the connection and no loss of time is occasioned by one having to wait for the other.

Suppose therefore that the operations described above have taken place and the A operator now plugs in. A circuit is thereby completed across leads 1 and 2 for both windings of relay 21 which is accordingly energized. Upon operating, relay 21at its armature 22 completes a circuit for the trunk busy lamp 24, which thereupon becomes lighted so as to notify to the tandem B operator that the A operator has plugged in. A circuit is also completed at Contact 22 for the polarizing winding of relay 23 and over the normally closed spring 25 of the busy key for the relay 20. Relay 20 thereupon operates, at itsarmatures 39 and 40 closes points in the speaking leads and at its armatures 28, 29, 30, 31 prepares circuits for starting the sending of impulses. In any one particular case however, only one of these circuits can be operative and since the first outlet is being used, a circuit; may now be traced from earth, armature 131 and its working contact, normally closed spring 117 of the sender disconnect key, lead 103, working contact and armature 17 working contact and armature 28, lead 104, winding of relay 121, working contact and armature 169 resistance 156 to battery. Resistance 141 is therefore short, circuited and relay 121 consequently energizes fully, thereby opera-ting its armatures 136, 137, 138, 130 and 140. At armatures 136, 137 and 138 the leads to the wipers 143, 1 14 and 145 are disconnected from the bankcontact s of the outlet finder and are connected to the leads 107, 105 and 104 respectively. At armature 139, the holding circuit is prepared and at armature 140 the circuit for relay 119 and for the assignn'ient lamp 27 is broken the assignment lamp therefore goes out and relay 119 commences to (lo-energize. The connection of dead earth from lead 10-1 over armature 138 to lead 167 brings about the energization of relay. 260 which energizes quickly and opensits contact 250 before the relay 202 has had timeto operate. 'The' relay 260 at armatures 247 and 249d1scona through to the impulsing contacts 269 and 270. At armature 248,- a' circuit is prepared for the relay :207, at armature 268 earth at armature 259 is connected to the holding lead168 and atarmature 252 a circuit is completed for relay 253. It :should be understood that relay 119 is slow to re lease so thatthe earth connection at its armature 131 may be replaced by earth at 'armature 259 without any discontinuity. I

Relay 253, upon operating, at armature 254 completes a circuit for the lower winding of relay 256 and at armature 255 completes a circuit for the release magnet 246 of the transfer. switch over the operated off normal contact'247. The transfer switch is thereupon released, the circuit of release magnet 246 being opened. at off normal contact 247 when the switch reaches normal position. When this occurs, a "circuit is completedfrom earth at off normal'contact 247, working contact and armature 248,

winding of relay 207 to battery. -Relay 207i operates, at armature 271' completesa look-- ing circuit for itself independently of the 011' normal contact, at armatures 212-215,

inclusive, disconnects the wipers of the transfer swit'chfrom the contacts of relays 202-- 206 andconnects themtothe converting relays 272, 273, 274 and 275 and at armaturev 216 completes a circuit for the impulsingrelay 280.- Relay 256 is a two-step relay similar to relay 121 and has a lightly ad usted armaso that the upper winding isfor the present short circuited. v

As soon as relay 207energizes a circuit is completed from earth, armature 259 andjits resting contact, working contact and armature268, working contact and armature-234,

first contact in the bank of wiper 226 and j said wiper,armature213 and its working contact,"relay 273 to battery, and a similar circuitmay be traced over the operated contact 235 of relay 231' forrelay 274. Relays 273' and 27 4 therefore energize and attheir contacts 277 and 278 openthe'energizing circuit of relay 253. This latter therefore releases and at'contact 254 removes the short circuit from the upper winding of relay 256 which thereupon operates all its ,armatures. At

armature 258 it breaks the connection to the tacts controlled by armature254, the oper-- ated relays are held up and'the opening of contact 259 has no immediate effect.-

Relay 273 also operates its armatures 281' and 282 and relay 27 4 operates its armatures 283, 284 and 285; a circuit is thereby com-- pleted from earth, armature 286 and its resting contact, armature 282 and its working contact, armature 284 and its'working contact to the contact in the lower bank of the impulse control switch corresponding to the digit 8. I

Since the circuit for the impulsing relay 280 was completed at armature 216 when relay 207 energized, relay 280 commences to energizeintermittently under the control' of the interrupter 287 which is driven at a steady speed and arranged to produce about 10 interruptions. per second. \Vhen' relay 280 energizes, it closes its contact 301," whereby the driving magnet 293 is energized" and opens its contact 270; since, however,

this is shunted by contact 269 no effect is produced at this time. Upon the following de-energization of relay 280, contact 301 is opened whereupon driving magnet 293 de-energizes and moves the wipers 289 and 290 one step. Wiper 289 then engages an across the outgoing trunk line which bridge ;may be traced as follows: from theupper ture 257 which is-operated when the relay is energized over one windin onlyv and" serves to connect earth to the ot er terminal talking conductor 37 through the normally closed contacts controlled by relays 13, 12

and 11, working contact and armature 14,

lead 105, working contact and armature 1'37,

" wiper 144, lead 166, armature 249 and its working contact, armature 270 and its restin contact, working contact and armature 24%, lead 165, wiper 143, armature 136 and its working contact, lead 107, armature 18' and its working contact, normally closed springs'controlled by relays 11, 12 and 13 to lead 38;'consequently an im ulse is sent out over the trunk line to the p istant selector. When the relay 280 again de-energizes,

the wipers 289 and 290 are advanced another step and upon the next energization a further impulse is sent out over the trunk line.

Relay-280 then continues to energize and deenergize under the control of interrupter. 287 until the wiper 290 reaches the contact in its bank which was earthed over the armatures of the operated converting relays 273' and 274. H d

When this occurs, a circuit is completed from earthjarmature "286 and its resting contact, armature 282 and its working contact, armature 284 and its working contact, contact in the upper bank of the impulse control switch, wiper 290,,through the winding of relay 291, to battery, and in parallel with this by way of armature 296 and its resting contact, armature 299 and its work-- ing contact to stepping magnet of the transfer switch. Relay 291, upon operating, at armature 296 opens the circuit oi the ste ping magnet 2 133 but not before it has ha time to operate, at armature 288 opens the circuit of the Limpulsing' relay 280, at armature 29S completes a locking circuit for itself and at armature 297 closes a circuit over the interrupter contact 295 for so; curing the automatic return of the switch to its home position, since driving magnet 293 now coi'itinues to receive current over wiper 289 until the latter engages the dead contact 294. \Vhcn this occurs the circuit for relay 292 is opened and it thereupon releases, at its armature ltlt] opening: the circuit of relay 291 which thereupon releases also. Both these relays. are, however, made slow to release so that an interval of t me is introduced sutllcient to allowol the auto matic hunting operation of the selector which has just been operated.

When relay 291 at length dc-el'icrgizes, the circuit for the in'ipulsing relay 280 is again completed at arn'iature 28S and a t'ur, ther series of impulses is initiated. however, the wipers of the tran: have been moved into second position and since relays 265 and 266 of the second storage set have been operated relays and. 274 of the converting relay set will cue! gizcd. Consequently the contact. correspondmg to the digit 6 will now be earthed in the bank of wiper 290 by way of armature 286 and its working contact, armature 281 and. its resting contact and armature 283 and its working contact.

before under the control of the interrupter 287, the switch taking one idle step before relay 292 is energized and relay 291 operatinp, and stoppingthc further transmission A5321. will then take place in a manner which will be readily followed from the .desa'rription that has already been; given, the transfer switch being advanced one step at the end of each series of impulses so as toibe in. a condition to control the succeedingseries. 1

When th transfer switch arrives at the 8th position, wiper 225 will encounter a i permanently earthed contact and conse- New, switch ceases.

The transmission of the second series ot nnpulses now proceeds as.

quent-ly relay 272 will be energized to con? trol the sending of a further train of one impulse which is additional to the number set up by the B operator. This impulse is employed inic-ase the call is going to a call indicator position to indicate to the operator.

there that the call she is dealing; with has come from the mechanical tandem exchange.

and not direct from an automatic subscriber. In case the call is going direct to automatic switches, this extra impulse will have no set of contacts are not wired, no circuits will be completed for any of the relays 272-275 inclusive and they will therefore all (lo-energize. A circuit is thereupon completed over the back contacts of these relays for the relay 253 which operates and at its contact 255 completes a circuit for release magnet 246 and at its contact 25etrcmovcs the lockin; earth which is holding up all the operated apparatus. The transfer switch therefore returns to normal and in conscquence of this removal of earth, all the opcrated storage relays are released and also the relays 260 and 256. T he release of the relay QGO breaksthe circuits for the relays 207 and i 253 at armatures 248 and 252 respectively and the clc-energization of relay 207 opens contact 216 so that the-sending; of impulses Relay 121 in the sender selector and relay 10 in the trunk circuit are also released and the sender guard lamp 164 is extinguished to indicate to the operator that sending has finished. Both the outlet and the particular sender used are now idle and available for use in setting up other calls.

The release of relay 1O completes the trunk circuitat the normally closed contacts controlled by armatures l4; and l8 and the wanted subscriber, if idle, will be rung automatically in the usual manner unless the con-j nectionis to a call indicator position. -When the called man replies, the flow of current over the line will be reversed at the back brldge relay of the connector according to usual practice and will then be in a direction to operate polarized relay 23. Relay 23,,

operator has made a mistake in. setting up.

the'number but discovers it before she has pressed .her start key. Infthis case she. will operate the cancel key 149; individual to her, position, the effect of which is to complete a circuit by way of armature 158 and its back contact for relay 159; Relay 1 59, upon operating, atarmature 160 completes a circuit for relay 157 which thereupon operates in turn and at armature 158 opens the circuit of relay 159 and completes a locking circuit vfor itself dependent upon the key 149- Relay 159, being sluggish, deenergizesslowly and it is thus arranged that relay 159 will always operate its contacts for the same length of time however long the -kev.- 149. is kept-pressed. Relay 159 ,atits contact .161, and similar contacts associated withthe other outlets removes earth at armatur 131 from wiper-146 and lead 168 so that the storage relay sets which have been operated for the digits already ,set up are released. When th relays 229-232 inclus ve,

of the first storage set de-energize, they com lete a circuit from earth at off normal contact 247 in operated position over back contacts and armatures 237, 238, 239 and 240 for the release magnet 246 of the transfer switch; this switch is thus restored, to normal in readiness to receive the; correct first digit. The operator may then 1mmed1- ately set' up the proper number and the sequence of operations will be as described above. I ,g I, In case, however, the operator has pressed. her start key and the sending of impulses has actually commenced before she. dis

coversher error, it will be necessary to operate the busy or cancel key associated with the junctionline which has been used. The

effect of this is to open the circuit of relay.

at spring and the locking circuit of relay 10 at spring26 whereupon both these I The de-ener'gization of relay 20 opens the contacts 39 and 40 where the loop across the outgoing trunk is opened and the switches which have been operated are released. The opening of convtact'28 removes from lead 167 the locking earth atthe normally closed springs controlled by armature 254 in consequence of which relay .260 de-energizes and the release of. all thel'operated apparatus in'the setof impulse sending equipment takes place as previously described. It will then be necessary for the operator to start the setting up operation from the beginning, that is to say, it will be again necessary to press the assign- .ment key anda different outlet and impulse show however, that should .the operator assign the line in error it will be impossible for an impulse sender to be. associated with it permanently and the lamp 27 will not glow steadily.

In case one ofthe outlets should be out' of order, it will be necessary to operate the associated sender disconnect key. At the left hand springs of this key the energizing circuit for relay 120 is opened at spring 114: and, at spring. 115 earth is connected tothc corresponding contact in the outlet finder so as to "prevent this particular outlet being taken into use. At the right hand spring of the key a circuit is completed for the sender guard-lamp 164 atthe spring 116 and at spring 117 the energizing circuit for the relay 10 is opened.

p The case whenall the senders accessible to a sender selector are busy is taken care of by achain circuit extending over one or more of the contacts 241, 242, 243, 244 in paralleland by way of lead 199 over one or more of similar contacts on the first storage relay set of the other impulse senders in the group to earth. When'all the impulse senders are in use therefore a circuit is completed for relay 118 which upon operating at armature 112 connects earth to lead 170, at armature 121 opens the energizing circuit of relay 120jand at the front contact of this armature connects earth to the contact corresponding to this ,outlet in the bank of the outletfinden, One effect of the connec- Hit) tion of earth to the contact with which wiper through relay 109, which is of very low resistance, also extends over lead 1.00, armature 19 and its resting contact, chain of. similar contacts on other assignment relays, armature 9 and its resting contact, lead lili/ 101, interrupter contact 124 to driving mags net 123; The driving magnet 123 therefore operates and advances the switch wipers one step into engagement with the next set of contacts. In case allthe sendersaccessible by way of this outlet are also busy, there will be earth on the contact. with which wiper 11 3 is now in engagement and the switch will continue to hunt until an idle outlet found over which the connection can be completed. 1

It might happen .in some cases that the outlet which has been preselected has access to only one idle sender and that while the associated sender selector is hunting for this sender it taken into use from some other operators position. It is clear that unless special provision were made the sender selector would continue to hunt until an impulse sender became tree and unnecessary Waste of time and wear of the switch would be occasioned. In this case also therefore it is necessary for the outlet finder to step on to find a new outlet but the circuit traced above is no longer operative since it is open atone oi the chain contacts; however this condition is taken care of by relay 109. \Vhen the assignment key is pressed, relays 108 and 109 are energize/(l as previously described in series with relay 120 and the sender selector conimences to hunt. When new all the senders in the group become busy, relay 118 operates and substitutes an earth connection at armature 131 for the connection to battery through relay 120. .llclay 109 is thereupon short circuited and at its armature 126 completes a circuit from earth, front contact and armature 122 of relay 118, armature 126 and its baclc contact, armature 1535 and its front contact, interrupter contact 124 to driving magnet 123. The outlet finder is thus automatically stepped on to find a tree outletand unnecessary hunting of the sender selector and waste of the operators time are avoided.

Referring now more particularly to Figures 5, 0 and 7 these show a modification of the arrangement illustrated in Figs. 2, 3 and 4. The chiefditterence between the two arrangements is that in Figs. 5, 6 and 7 the outlet finder and sender selector switches have five wipers and in consequenee it is )ossible to dispense witlrthe converting relays which were connected to the wipers of the sender selectors and to operate the storage relays direct. In addit-ion various small iniprovements have been incorporated, such as the provision of I flashing signals to indicate to the operator the progress of the connection and an arrangement for obviating the possibility of two operators seizing the same set of impulse sending equipment. These additional features will be more fully understood from the following detailed descrip tion of the operation of the apparatus.

As before the B operator is informed over an order wire of the required number and she then assigns an idle junction line,

by way of a chain of contacts such as arma ture 311 on all the assignment relays to lead 400 which extends to erpiipment individual to the position lets.

The effect of this earth connection is to energize the relays -l08, 1-09, 410 and 420,

the circuits for the two last extending from earth on lead 400, winding of rela 110, wiper 460 and the contact with whic 1 it is in engagement, normally closed spring 462 of the sender disconnect key, armature 184: and its back contact, relay 420 to battery. Relay +t08 operates its armature 452 and 453 thereby closing contacts for a pm ose which will be fully described hereai'ter. Relays 409 and 410 at contacts 165 and 466 control the circuit of thedriving mamiet &67. As however relay 409 is slightly slow to pull up, contact 486 will always be opened before contact s closes and a cir cuit will in the normal course of operation never be completed for magnet 467, even should earth be connected to lead 469 which will not in general be the case. Relay 420 upon energizing, at armature 432 completes a circuit for cut off relay 419 and driving magnet 145 in series which circuit may be traced as follows: earth, resting contact and armature 4:92, armature 456 and its resting contact, wiper 4th and the contact with which it is in engagement, armature 1? 2 and its working contact, armature 432 and its working contact, winding of relay 119, interrupted contact 446, driving magnet 1-15 to battery. Relay 420 also at armature 433 connects the test wiper 4:74 of the sender selector by vay of resting contact and armature 151 and armature 431 and its resting contact to the junction of relay 119 and driving magnet P15 iirthe above circuit. Consequently if there is an earth on the contact with which wiper 174 is in engagement, relay 119 will be short circuited and the switch will commence to hunt in the usual manner until wiper 474 engages with a conta -t which is not earth-ed.

\Vhen this occurs, relay 419 will encrgize in series with driving magnet 45, which latter, however, does not now receive enough current to energize it. Relay 419 At the same time she presses and common to all the out upon operating, at armature 430 completes Relay 418 uponoperating, at armatures. 424,

425 and" 426 connects the wipers 456, 457 and 458 throughto the wipers 470, 471, 472 respectively, wiper 459 having previously been connected through at armature 428 by the operation ofrelay 419. At armatures 475" and 427, battery and earth respectively are connected to leads 402 and 403 ext ending to the trunk c1rcu1t,the earth connection to lead 403 being over the normally closed spring 4640f the sender disconnect key. A branch circuit from this spring also ex tends to thesender guard lamp476 which therefore lights and indicates thatthe cor-' responding outlet is in use.

The effect of the connection of batteryand earth to the leads 402 and 403 is to complete an energizing circuit for thetrunk connect- "a ing relay 312 which circuit maybe traced from the battery connection on lead 402 by 'way of the normally closed contacts controlled by armature 320, winding ofrelay 312 and armature 305 and its working contact to earth on lead 403. Relay 312 therefore opcrates, at its armatures 316 and 317 connects the, outgoing trunk conductors 336 and 337 to the impulsing leads 405and 407, and at armature 318 completes'a circuitfrom the normal battery connection on lead 406 by way of resting contact and armature 439 to the assignment lamp 322, armature332 and its resting contact and flashing interrupter. 333 so that the. assignment lamp 322 com-' mences toil-ash. Relay 312 also at armature 319 prepares an energizing clrc'uit'tor relay 338, at armature 320 opens lts initial energizing circuit and completes a locking circuityfor itself by way of the normally closed.

spring 326 of the busy or cancel key and at armature 321 shunts armature 306 so that its own circuit is not interrupted when relay 305 deenergizes upon the release of the assignment key 304.; The operator keeps the assignment key pressed until the lamp 332 lights, whereupon she knows that the outlet tinder and sender selector switches are functioning correctly and that her key set is now crninected to an idle set of impulse sending equipment.

The apparatus is now in readiness for registering the wanted number as set up upon the key set. Suppose that tlienumerical equivalent of the "wanted number is 8765432. When the'key 8 is pressed,a circuit is completed from earth, operated spring of digit key 8, lead 480, wiper 457,

and the contact with which it is in engagement, working contact and armature .425, resting cgntact @Imature 440, W;1per-471,

result.

lead 501, armature 526 and its resting con- I .the earthed lead 504. Since, however, the

lower winding is now short'circuited by an earth connection, to both its terminals,ithere is no further. operation of relay 5'08at this time. Relay 538, however, operatesfully; at armature 539 completes a circuit for relay 550, at armature 540 opens a point in the circuit of the stepping magnet 5510f the transfer switch and at armature 541 opens a point in the circuit of relay 552. .Relay 550 energizes when its circuit is completed and at armature 543 prepares a circuit for the stepping magnet 551. A similar circuit is also completed from the other operated spring of the digit key 8, which circuit extends over lead 481, wiper'458 and the contact with which it is in engagement, working contact and armature 426, resting contact and armature 441,'wiper 472, lead 502,-armature 527 and its resting contact, resting contact and armature 533, wiper 546 of the transfer switch in first position, lead 553,

armature 554 and its resting contact,upper removed from the middle'point of the windings of relays 508 and 509 and these relays accordingly both energize fully through their two windings in series while relay 538 'is'de-energized Relay 508 upon operating,

at armature 512 closes a point in a chain circuit'for a purpose which will be explained hereafter, at armature 516 opens a point in the circuit of release magnet 557 of the transfer switch, at armature 520 opens its initial energizingfcircuit and completes a locking circuit for itselfand at armature 5 19 connects earth from lead 504to the corresponding contact in the bank of wiper 545. The operation of armatures 513, 517, 5.55, and 554 of relay 509. produces; a similar When relay 538 deenergizes, armature 540 engages withits resting contact and since relay 550 is made slightly slow by providing I it with a short circuited winding, a. circuit is now completed which'extends' from earth,

till

resting: contact and armature MU. steppiiui magnet 551. to battery; the transfer switch is thus moved on one step into engagement with its second set of contacts.

.The operator will now press the key for the second digit 7 whereupon a circuit is con'ipleted from earth. operated spring of digit key 7. winding of relay 482 to battery. Relay 4:82 at its armature -18?) completes a circuit as follows: earth. working contact and armature 4S5, wiper no and the contact on which it standing. working contact and armature 4524. wiperi'r'tl, lead 500. armature and its resting contact. resting contact and arn'iature 536. wiper 544: in second position over resting contact of relay .358 similar to contacts 519 and 554, upper winding of relay 558, normally closed springs controlled by an armature similar to armature 520. testing contactand armature relay 533 to battery. Relay 558 thereupon operates its light armature and when the key released operates fully. producing: results si1uilar to those described in connection with the first set of storage relays. Relay 538 encr gizes as before and jointly with relay 550 controls the stepping: on of the transfer switch when the digit key 7 is released.

A circuit also completed by the operation of key 7 from earth, operated spring of key 7, lead L79, wiper 459. workii'ie contact and arn'iature resting contact and armature 442, wiper 473, lead 03. armature 528 and its restingeontact. r inn contact and armature 534. wiper 547 and the second contact in its bank through the upper winding of relay 559 and relay 538 to battery. A branch of this circuit extends over resting; contact and armature 541 to the windine' of relay As however, relayfihfl is slightly slow to pull up and its circuit is at once opened by theoperation of relaylii-ls it does not energize at this time. i

As a result of the ncssitu. oi the digit key 7 for the second digit therefore. relays and 559 have been locked up and earth has been connected to the second contacts in the hanks of wipers flit-l and 547. As previously stated the. transfer switch is stepped on when the key 7 is released and moves into position i) so as to connect up the third storage relay set. The operation of setting up the remaining digits will readily be tollmrcd. from what has already been described and need not be traced in detail. 7

After the seventh digit has horn sent. however. the transfer switch will he stepped on into the eighth position in the usual manner but when relay 550 deenergizes a circuit may he traced as follows earth. resting'contact and armature 560. eighth coutactin the hank of wiper 5H and said wiper, armature 536 and its resting contact. resting contact and armature 525. lead 500. wiper 4T0. armature 424 and its working Contact. wiper ing contact. normally closed spring 45c, armature 485 and its resting contact, winding oi. relay 4-86 to battery. llelay 486 thereupon at once energizes and at its armature i818 completes a circuit for stepping u'iagnet 4-(3'1' and at its armature tl-ST crunplctes a. circuit for start relay 4-89. iltepping magnet 467 then moves the wipers ot the outlet tinder one step into con act ment with the next outlet whereupon the circuit for relay 486. is opened and the relay ('lcencrgizes. Start relay 4:89 energizes when its circuit is completed and at its armature ti/0 completes a circuit for relay 422. It will be noted that relay 485) has a pair of contacts for each outlet but clearly since it only one outlet can he used at a time. only one of these pairs of contacts will in each case perform any useful function, Belay 422 upon operating, at armature 438 completes a locking circuit for itself independent of armature 4-90. at armature 4237 reinorcs the hattery connection from lead 4-02 so as to prevent any other trunk relays as- SO'TltllBtl with this outlet from energizing when the next assignment key is pressed, and. at armature 42o prepares a circuit for relay el-Qi}.

It should he noted that withthe arr-anciement described. it the operator sends the tall seven digits which is the maximum for which the arrangement is designed (though obviously comparat-irely slightaltcration is necessary to enable a larger number to he dealt with). no special operation on her part is HPCPSSHFX in order to initiate the actual scndine of impulses. since the relay 4-86 pertorms the same function as the start key 48;}. it, however. a less number of digits is hcinn sent. all the required operations can he made to take place without any alterations to the apparatus. the only difference being that it will now be necessary for the operator to press the start key when she has set u all the required digits. in the same manner as as done in every case in the arrangement descrila'd in Figs. 3 and l.

For the sake of convenience it will he again assumed. as in describing: the previous arrangement, that the pressing of the start key or etpiiralent automatic mieration takes place before the A operator has ])lll;1;,[(tl in. \Vhen she does so a supervisory circuit completed over the lower talking; conductor ill)? and the normally closed spring il -h ol' thecnicrgcncy order wire key for relay 37in. Relay 3-39, upon operating. at its armature IMO completes a circuit for the polarizing; winding of relay 34-2 and also a circuit for relay 338 which latter circuit extends as follows: earth, armature 3-10 and its work- 7 325 of the busy or cancel key, working contact and armature 319. relay 338 to battery. Relay 2338. upon operating, at its armatures 38 and 335 closes points in the outgoing tifiink ltlll ltlu neamo leads, at its armature 327 completes a. look ing circuit for itself, atits armature 332 substitutes a direct earth connection for the earth connection by way of the flashing in terrupter and at its armatures 328, 330 and 331 prepares circuits for initiating the generation of impulses. As previously explained, only one of these circuits will be usefully operative'at a time. In thiscase the oint operation of armatures 332and 341 completesa circuit for the trunk busy lamp 323 and the assignment lamp so that thelatter, which haspreviously been flashing under the control of'the flashing in terrupter 333, will nowglow steadily.

' In consequence of the operation of 3111121 ture 328 a. circuit may now be traced from earth, armature 427.'.and its working con tact, normally closed spring 464 of the sender disconnect key, lead 403, working contact and armature 321, working contact and armature 328, lead 404, armature 436.

and its working contact, winding of relay 423 to battery. -'Relay 423 therefore ener gizes and uponoperatingmt its armature-s: 440, 441 and 442 connects the wipers 471, 472 and 473 to the'leads 407, 405 and 404 respectively. Furthermore at armature 43) it 'reinoves'the battery connection from lead 406 so that the assignmentlamp 322 is ex t-inguished, at armature 443 prepares the holding circuit and armature 444 opens the circuit for relay "Relay 419 slowly deenergizes and at armature 429 opens the circuit for relay 418 which also slowly dccnergizes. V

The connection of earth to lead 503 by way of the'resistance 495 completes a circuit by way of resting contact and armature 541 for relay A'branch; of this circuit also extends over armature528 and its resting contact, resting contact and armature 534, to wiper 5 47, but since 'thiswipcrisin en- I gagement with the eighth contact,which is dead, clearly no effect can be produced. it may happen, however, the operatoris desirous of transmitting less than the"maximum number of digits i. e; 7, that the wiper 547 would not be standing on the eighth contact buton one which was connected to a relay of a storage set and obviously it'- this relay has not previously operated it mustnow do so. It is tor thisreason that the resistance 495 is-inserted, relay'552, however, being arranged to operate in series with this resistance. @Relay upon opcrating, atits arn'latures 526, 527.;and 528 disconnects'the leads 500, 501.502, 503 from the wipers 544, 545, 546 and 547 re-- spectively, of the transfer switclnat armature 529 prepares a circuit for relays 530 and 531, at armature 561 places earth by way of armature 573 on the holding lead 504 and at armature 562 completes a circuit for relay 567 by Way of resting contacts armature 570, release magnet to battery,

. to normal.

and its resting contact, armature 561 an! 573 is connected to holding lead 504 before; it is removed at armature 427 even though 70 relay is slightly slow to pull up.

Relay 567 upon operating, at armature 570 completes a circuit from earth, operated off normal spring 575, working contact and whereupon the transfer switch is restored Relay 567 at'arinature 569 com I pletes acircuit for the upper winding relay 568 which is thereupon par ially energized and operates its lightly adjusted mature 571. Earth is thenconnected to the other terminal of the upper winding of relay 563 so that this winding is for the present shortcircuited. As soon as the transfer switch reaches normal position, a circuit is completed from earth. normally closed spring 574, working contact and mature 529, relay 531, relays 530 to battery. Relays 530 and 531cnergize in series and the former at armature opens the ener ing circuit for the storage relays so as to prevent any subsequent accidental operation and at armatures 533 and 534 connects wip- 'ers 546'and 547 to the converting relays 523 and 524. Relay 531st its armature completes a locking circuit for itself and relay 530, at itsiarmature 542 closes a circuit for nnpulsing relay 578 and at armatur 536 and 537 connects wipers 544 and 522. Since the relays508 and 509 of first storage set havebeen operated, a 1' cult 1S now completed from armature l its working contact, working contact and armature .519, lead 548, firstcontact in the bank of Wiper 545 and said wiper, armature 537 and its Working contact, relay to battery and asimilarcircuit may be traced over working contact and armature 554, lead 553, fir st contact in the bank of wiper 546 and said wiper, armature and its work ing contact, relay 523 to battery.

The resulting operation of relays 522 and T23 opens the circuit of relay 567 at armatures 564 and 565 and relay 567 consequently deenergizes. A further earth is thereupon placed on the holding lead 504 at the normally closed contacts controlled by armature 569 and at the same time earth is removed "from the middle point of the winding of relay 568. This relay thereupon operates fully, at armature 572 breaks the connection of the middle point of its winding and at armature 573 removes the parallel earth "from the holding lead 504. I I The sending of impulses now commences and will proceed as described in connection with Fig. 4. Relay 578 is intermittentlyv energized and deenergized and accordingly 160 p .ated when the impulse control switch takes 5 its tirst step and thus produces correspondinn interruptions in the circuits of the line relays of the various selector and connector switches.

Tn this case also provision is made for sending aapecial impulse to a. call indicator postion alter the seven digits set up by the ll operator have been transmitted. This is brought about by the earth connection over resting contact and armature 560 to the eighth contact in the bank of wiper 54.4 and the operation is similar to that. described in the previous case.

The release oi the various operated relays after all the digits have been sent also takes place in :1 manner similar to that described before. the holding earth being removed from the lead 50 1 at the normally closed springs controlled by armature 569 when relay 567 again operated due to the deenergization of all the converting relays F521, 5 523. 524.

in case the operator makes a. mistake in setting up the wanted number and discovers it betore the COll'lPlLtG number has been set up, that is, before the operations corre sponding to the pressing of the start key have taken place, she is; enabled to cancel. the digit already et up by pressing the cancel key 484. This brings about the moinentary o 'ieration of relay ell-8 and the ()PQIiItlOl'l of relay 4-47 as lone: as the key is kept pressed. Relay HS upon energiw ing. at its armatm'e L51. removes earth from the holding lead 504 thereby releasing all the operated storage relay. and at its armature {lilo removes earth from wiper so as to prevent another operator from seizing); this set of impulse sending eqilipment during the momentary removal of earth from test wiper 4-74. In case the sending oi impulses has actually commenced she will as in the previous arrangement. press the busy or cancel key associated with the trunk line which baa been taken into use. the etlect of this being to open the locking: circuit tor the relays $338 and 312. thereupon on the deenergizaatioii of relay 33s. the lurking" earth for relay [iii-2 is removed at armature 311M an that this relay decncrniues and reall the operated a maratus in the set o't unpuhie vending equipment as in the or-- dinary course. The operator will then press the assignune' il hey Sill attain whereupon another impulse sender set will be seized and the commotion may be completed in the ordinary way.

The emergency order wire key is provided in order to enable the inter-exchange junction line to be used as an order wire in case '5 of necessity. hen the. key is operated the connections of conductors 302 and 303 to the trunk circuit relays are broken at springs 3114b and 34.8 and these comluctors are connected at springs 3a? and 34%) to the leads 351 and which can be extended to the operators head set. At spring 350 a circuit is completed for the trunk busy lamp 323 which is thus lighted to indicate to the operator that the trunk line is not a "ailahle for use.

It may be desirable at this point to explain the precise nature and operation of the lamp signals which are provided to indicate to the operator the progressot the connection. As has already been explained, tlltMOIXlllhOl' holds the assignment key pressed until the assignmcntv lamp lights. If the A oporator has not already plugged. in, the lamp 2-322 will glow intermittently under the control of the flashing interrupter 3323, and will continue to flash until the A operator does plug in. after which it will glow steadv ily until the sending;' of impulses connnences. At the same time the sender guard lamp 4176 will light and glow steadily to indicate that an outlet is in use. As has been pointed out it the A operator is a. trifle late in plugging in, this operation will control the starting of the sending of impulses and con sequeutly in this case the lamp 322 will continue to flash until itis extinguished.

The trunk bi'isy lamp 3:2 will always be lighted when the A operator plugs in; in case the B operator should not vet have pressed her assignment key, the lamp will flash until the key is pressed. and an idle impuse sender is found whereupon it will glow steadily and continue to do so until the connection is taken down. By means of theselamp signals the operator is kept l'ully intormed ot' the progress of the connection except that she is not given answering supervision when the calling subscriber replies as this is clearly unnecessary. The sender guard lamp 476 will remain lighted as long as the particular outlet is in use or the sender dis. connect key is operated. This is similar to those )rovided in the previous arrangement and when operated lights the sender guard lamp and prevents the particular outlet from being ta hen into use. Tl arrangement of relays 4-09. -1ll(l and -l-2l is the same as that previously described and has tor l'unction the preselcction of an outlet haviup, EHQPRH to an idle impulse sender and the moving on of the outlet tinder in case all the senders in a particular group should become busy alter the assigmiient key has been pressed. The chain circuit for en-- ergizing relay 421 extends over contach; an, 512, 513 and 514 in parallel and over similar contacts on otherfirst storage relay'sets .in the group to earth. 7

A description may now be given oi the apparatus shown in the lower part. of Fig.

ltll) 1 Il t) i to ill

6, the object of which is to obviate the possibility oltwo operatorsseizingjthe same impulse sender at the same time The relays surh as 408 are individual to each operations position and each is connected to the lead correspomiii to-lcad 400 so that it will encrgizeu'ln ier any unein' ey the position is pressed. lt l Y 405; ((lTll'l'OL; t YO armatures 4152' and 4: chefv circuits which include contacts controlledlay-the relays smnlarto s08 associated with all the other positions having access to the same group of impulsesendcrs. The former of these circuits comprises a closedrircuit es:-

' tending through the armaturcs and ha cl: contacts, While the armatures are also con ccted to appropriate contacts in the hunk of Wiper The trm tjctuitacts of these armature; extend to armatures such as 432 and are thus included in the energizing circuits of the cut-oft relays such as 419. it. will he remembered that the circuit for relaytlt was tracec from earth at resting contact and armature 492, chainoi similar ,contactson other cancellin relays, armati'u e and its resting; contact, Wiper {Hi and the contact with which it is in engagement, armature i552 and its Working contact to relay 4H9. It will he seen-that lilfOflly' one relay as 408 is operated at a timeand the 455- is in a different position from that i shown, a ciri'iuittor-relay lids-rill still he completed over the armatures such as 452- ;and their back contactsw-w hen, hornet-er,

there ismore than onerrelay 408 operated at a time in which case Wiper 455 Will he rotat-a ing, as aboutto be explained, circuits for relay. such as4tl9 will only be completed in turn. aswiper455 comes into engagement with the contact connected to the immature controlled by the particular relay. By this none or only one ot the relays 408 is o; er-

atcd, a circuit will not bet unpleteil driving magnet itl of VVlQQE'I 455 but as soon as two or more of theserelays-are o a circuitis completed and consequez and the lite ot' the switch is correspondingly hene' lent u. ,The relays lOSWill only he op rated as long astheoperator keeps her a;;si;gn'ment key prefised and thus it is by no means unlikely that, even a in e number of operate. s, only onemay he n p wvithan idle register sender.

In, order to-arran e th t r P i one of Wiper 455 is started up. By thislmeans ll1lnecessary rotation of iper 4:55 is avoided ing an assignment key atany particular instant.- The earth-connection tothe iper 5 is takenthrough additional'contactson the cancellation relays such as .448 lIl'Qlclef at it an operator presses heriancel key 481' whereupon earth fisf momentarily removed an the multiple testcontactinthe hank 0t Wiper Hat, no other operator Will be 'ahle Y to seize the impulse senderwhich'has been taken into use and itc'anhe used again tor setting up the proper annnber and thetranS- mission of the required impulses e It'has beenarranged both in the arrangement shown in Figs Q', 3 and 4t andinthe arrangement shown in Figs. 5, 6 and '7;tha t the sending of impulses does notcomnieiu'c until the A, operator plugs in, since this in general desirable. a It should be understood however, that this "is not essential to the Working or the arrangement and tl1at-,hy eliminating the starting contacts on the relays20 or-338and substituting direct con nections, the starting of the generation of impulses may be placed under the sole control of the B operator at thetandem ex change, J i

Having now particularly described: and

ascertained the-nature cit-our said invention and n What manner the same is to be performed, rite-declare thatzwhat We claim'is:

1. Ina telephone system, arplurality of trunk l1nes,an assignment key-individual to each of said trunk lines, a plurality of register senders, a plurality of operators link circuits, an operators key set, and means responsive to the operation of oneof said assignment keys for connecting said key set to an :idle link circuit and for connecting said ldlQClIfClllt with the assigned trunk line and 2. In atelephone s'yst.em,-a plurality ot trunk lines, plurality of link circuits,; a plurality of register senders,-a key; set, means including a :itorivard huntin j-switch individual to said key set for connecting said key I set with an idle oneoii said link circuits, operator-cont'rolled means foreonnecting said idle link circuitiyith an idle trunk line, and

a. hunting switch for effecting a connection between the last named link circuit and an idle senden J,

In'a telephone system, a plurality of trunk lines, a plurality of link circuits, .a plurality ofregister senders, a key set, a forwvard-hunting switch individual'to said key connecting saidkey'set withan'l idle set for I saidlink circuits, and operator controlled means-torefi'eeting a connection between said idle link circuit and an idle trunk line and for eil'ectin a connectionbetweensaid link circuit and an idle register sender.

4; In a. telephone system, it] plurality of trunk lines, a plurality of register senders,-a plurality of link circuits, anjoperators keyset, means for connecting said key set With an Hit) 

